AC-3632::'Price drop' Product Alert for Simple product mail not coming to customer

Author: faizan-shk

lib/internal/Magento/Framework/Filter/Input/MaliciousCode.php

@@ -61,7 +61,7 @@ public function filter($value)
     {
         $replaced = 0;
         do {
-            $value = preg_replace($this->_expressions, '', $value, -1, $replaced);
+            $value = preg_replace($this->_expressions, '', $value ?? '', -1, $replaced);
         } while ($replaced !== 0);
 
         return $this->purifier->purify($value);

lib/internal/Magento/Framework/Filter/Test/Unit/Input/MaliciousCodeTest.php

@@ -146,6 +146,7 @@ public function filterDataProvider()
                 '<?=$test?>',
                 '',
             ],
+            'Null Value' => [null, ''],
         ];
     }